DE 39 31 116 A1 (Krupp Polysius AG) discloses a drive arrangement for a roller mill comprising a ring gear and an axial bearing, wherein the axial bearing is located directly beneath the ring gear. The ring gear meshes with two pinions of an ancillary transmission. The ancillary transmission further comprises a spur gear coupled to said two pinions and a bevel gear, wherein the bevel gear is coupled with a pinion of a motor. While such a configuration of the mill allows a reduction of the total height of the mill, the drive still relies on a horizontally mounted motor and hence needs a bevel gear to transmit torque from the motor into the ancillary transmission.
DE 102006050205B4 (Gebr. Pfeiffer AG) describes a redundant drive arrangement for a roller mill comprising a plurality of independent drive units mounted on carriages. Each drive unit comprises a motor as well as a spur gear. The number of drives installed in a mill is selected such that the mill may be used even if one of the drive units fails and has to be repaired or replaced. The motor may either be arranged horizontally, which requires an additional bevel gear to transmit torque to the spur gear or arranged vertically within a cavity provided in the fundament of the mill.
CH 672 603 (Maag Zahnräder & Maschinen AG) discloses a bowl mill drive comprising a motor with a vertical drive shaft which acts on a spur gear by means of a pinion. The motor is arranged above the spur gear. The spur gear comprises a plurality of wheels and finally transmits the torque to a grinding bowl via a shaft and a planetary gear arranged beneath the grinding bowl.
As only small tolerances for bevel gears are acceptable at such high loads, high precision is needed when producing and mounting the bevel gear which results in high overall costs of the drive arrangement. Further, angular vibrations as well as recoils during operation of the mill may damage the gear arrangement or the motor or at least increase the wear of these parts.